Re: [PATCH bpf-next v2 0/4] Add ftrace direct call for arm64

[Florent Revest]

On Wed, Oct 5, 2022 at 5:07 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> On Wed, 5 Oct 2022 22:54:15 +0800
> Xu Kuohai <xukuohai@xxxxxxxxxx> wrote:
>
> > 1.3 attach bpf prog with with direct call, bpftrace -e 'kfunc:vfs_write {}'
> >
> > # dd if=/dev/zero of=/dev/null count=1000000
> > 1000000+0 records in
> > 1000000+0 records out
> > 512000000 bytes (512 MB, 488 MiB) copied, 1.72973 s, 296 MB/s
> >
> >
> > 1.4 attach bpf prog with with indirect call, bpftrace -e 'kfunc:vfs_write {}'
> >
> > # dd if=/dev/zero of=/dev/null count=1000000
> > 1000000+0 records in
> > 1000000+0 records out
> > 512000000 bytes (512 MB, 488 MiB) copied, 1.99179 s, 257 MB/s

Thanks for the measurements Xu!

> Can you show the implementation of the indirect call you used?

Xu used my development branch here
https://github.com/FlorentRevest/linux/commits/fprobe-min-args

As it stands, the performance impact of the fprobe based
implementation would be too high for us. I wonder how much Mark's idea
here https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/ftrace/per-callsite-ops
would help but it doesn't work right now.